The present invention generally relates to proximity sensing and, more particularly, to a housing for a proximity sensor which is resistant to environmental effects, such as slag build-up that may occur in a welding environment.
Various types of proximity sensors are used for detecting the presence or absence of an object. Common types of non-contact proximity sensors include inductive proximity sensors, capacitive proximity sensors, ultrasonic proximity sensors, and photoelectric sensors. Such sensors, for example, may be used in motion or position applications, conveyor system control applications, process control applications, robotic welding applications, machine control applications, liquid level detection applications, selecting and, counting applications, as well as other known applications.
In an inductive proximity sensor, for example, an oscillator provides an oscillating signal to an inductive coil, which provides an electromagnetic field at a predetermined frequency. As an electrically conductive object moves within the field, eddy currents develop within the object in response to the oscillating electromagnetic field. The eddy currents alter the amplitude of the oscillating signal being provided to the coil. The amplitude of the oscillator signal typically is evaluated to provide an output signal indicative of the presence or absence of the object within the electromagnetic field.
Proximity sensors often are employed in manufacturing industries in which the sensors are exposed to harsh environmental conditions. By way of example, proximity sensors are utilized in conjunction with robotic welding to sense the position of work pieces and/or robot components during welding processes. The welding environment subjects the sensor to abrasion, chemical exposure, intense heat, and scorching particles that cause slag build-up. The environmental effects cause the sensor to deteriorate rapidly and eventually fail.
In order to help protect proximity sensors from such adverse effects, manufacturers utilize a Teflon coating or covering around the sensor. A typical Teflon coating is on the order of a few microns thick. While the Teflon helps mitigate damage to the sensor, the environmental conditions wear through the Teflon over an extended period of time, thereby exposing the sensor to the adverse environment. For example, there is substantial sputtering of molten welding materials which tend to contact the sensor housing and cause slag build-up. As a result of slag build up and other damage to the housing, false triggering (due to a change in sensing capability) and, in turn, premature sensor failure may occur. Once a sensor is unable to operate within acceptable parameters its replacement is imminent.
There are inherent difficulties associated with replacing a proximity sensor in a harsh environment. Replacement of a proximity sensor presents a significant safety concern to the technician performing the repair, as it may subject the individual to undesirable risk of exposure to the precarious environment. In order to reduce the risk, it may be necessary to temporarily interrupt or stop the manufacturing process, which results in undesirable and usually expensive down time in the manufacturing process.
The present invention relates to a housing for a proximity sensor that is resistant to harsh environmental effects. The sensor housing is formed of a material having a high thermal conductivity. The housing is able to rapidly dissipate heat, such as due to contact with scorching materials sputtered during welding. Because the housing effectively dissipates heat, it mitigates slag build-up which, in turn, improves the efficacy of the sensor. As result, a sensor having a housing in accordance with the present invention may experience increased longevity in challenging industrial environments.
An aspect of the present invention provides a proximity sensor. The proximity sensor includes a housing which contains circuitry for sensing proximity of an object, wherein the housing is formed of a copper material.
Another aspect of the present invention provides a proximity sensor. The proximity sensor includes a sensor housing which contains sensing circuitry for sensing proximity of an object and providing a signal indicative thereof. The sensor housing is formed of a material having a thermal conductivity of at least greater than about 3 Watts per centimeter per Kelvin.
Still another aspect of the present invention provides a housing for a proximity sensor. The housing includes an elongated cylindrical sidewall portion for receiving sensing circuitry therein. The sidewall portion is formed of a copper material having a high thermal conductivity, whereby when the housing is employed in a welding environment slag build-up is mitigated.